sound energy has been applied to tissue for various thermal treatments and has been used in mechanical actuators based on motion/deformation of a piezoelectric element. Separately, heated fluids have been employed in the thermal treatment of tissue such as ablation. For example, in hydrothermal ablation, fluid heated to approximately to 90° C. is introduced into the uterus to ablate the lining thereof. To ensure even temperature distribution, this fluid must be agitated and circulated within the uterus via, for example, an external heater and pump. The fluid is heated as it passes through the heater while being pumped in a cycle into and out of the uterus. However, as this fluid circulates in and out of an organ such as the uterus, tissue particles in the fluid may become lodged in the external heater or the pump reducing the circulation of the fluid and the uniformity of the ablation of the endometrium.